c - Correct way to allocate memory for structure? -

i trying determine best way allocate memory dynamic number of pixels read file. have number of bytes of pixel data header file.

i trying in following way, missing something.

typedef struct {     unsigned char blue;     unsigned char green;     unsigned char red; } pixel_t;   for(i = 0; <= ((bmp->dib.bmp_bytesz) / 3); i++) {     // here? }    

well, memory allocation doesn't go indicated:

pixel_t *pixels = malloc(((bmp->dib.bmp_bytesz/3)+1) * sizeof(*pixels)); if (pixels == 0)     ...deal out of memory error...  (int = 0; <= bmp->dib.dmp_bytesz/3; i++) {     pixels[i].blue = ...;     pixels[i].green = ...;     pixels[i].red = ...; } 

the +1 allows <= in for loop. careful check <= correct; more usual use < in for loop.

---

for ..., if have pixels in char array? how can step through , copy pixels?

you can in either of couple of ways. assuming pixel array in unsigned char *pixel_array;, use:

unsigned char *p = pixel_array;  (int = 0; <= bmp->dib.dmp_bytesz/3; i++) {     pixels[i].blue  = *p++;     pixels[i].green = *p++;     pixels[i].red   = *p++; } 

or:

for (int = 0; <= bmp->dib.dmp_bytesz/3; i++) {     pixels[i].blue  = pixel_array[i*3+0];     pixels[i].green = pixel_array[i*3+1];     pixels[i].red   = pixel_array[i*3+2]; } 

just make sure blue, green, red sequence correct.